Patent GB-1292398-A (GB)
Title: A telecommunication exchange system
Inventor: REANEY DONALD
IPC: H04Q3/54
Filed: 1970-07-29
Abstract: 1292398 Automatic exchange systems PLESSEY CO Ltd 13 July 1971 [29 July 1970] 36624/70 Heading H4K A number of exchange units 1, each serving and interconnecting a group of subscribers by means of a duplicated control circuit employing semi-conductor circuits and reed relays, are worked in parallel with means whereby subscribers may gain access to subscribers to other units, incoming lines 2A-2N being distributed to the units by a network 2 and outgoing lines 3A-3N being accessible to the units over a network 3. For inter-unit connections the network 3 may give access to incoming junctions of the units 1, as shown in Fig. 1; alternatively, each unit 1 may be strapped over other-unit outgoing junctions to incoming junctions of the units 1, Fig. 2, not shown. If the system is part of a director system, a common code translator 4 is provided. STD and "0"-level calls are made over main exchange junctors 5. Exchange units.-These are of the kind described in Specification 1,093,637 and known under the Trade Mark "Pentex" or the code TXE2. Subscribers lines 7a, Fig. 3, terminate on circuits 7 and in the calling condition activate an identifying wire 7b threaded through cores of identifier 20. The so-provided calling number is stored in 21 and steered by allotter 22 to a register 28 seized by control circuit 24, for the call. The register 28 stores particulars and advises renter 23 of requirements. Control 24, however, initially assumes that an outgoing relay set 12 is required and sets up a connection over the A, B, and C, stages of relay cross-point switches 8, 9, 10 between the calling line and a free set 12, the register 28 being connected to the set 12 by way of the register connector 29. If received digits indicate that a main exchange connection is required over junctions 5, Fig. 1, register 28 releases and digits are sent direct over the junction. If received digits indicate an own-unit call, the selected outgoing relay set 12 is released and a new connection is set up to a free own-unit relay set 13. Given the wanted own-unit number the register 28 marks the line circuit of the wanted line by application to a decoder 26 and strapping field 27. A connection is then set up between that line, supposing it tests idle, and the relay set 13, by way of stages A, B, C, and D, shown as 8, 9, 10, 11. Release is immediate to calling party disconnection and is enforced after 3 minutes if only the called party disconnects, busy tone being connected to the still off-hook calling instrument. In the event that the called line is found busy or unequipped, number unobtainable tone is returned and the connection is forcibly released after 20 to 40 secs. if the calling line is not cleared. Incoming calls appear at incoming relay sets 14 and are given priority by control circuit 24. Identified in 20 and allotted a register 28 the calling set 14 is marked over strapping field 27 and connected to the register 28 by way of connector 29. Acquainted with particulars the register directs connection as for terminating a local call. The calling number store 21 is a ferrite core store. Incoming traffic distributer.-Fig. 4 shows the incoming junctor circuits 30 connectible over relay cross-point switching stages A, B, C, shown as 31, 32, 33, to relay sets 34 giving access to incoming junctors of the exchange units 1. The network is "planed" so that each junctor 30 has access to a group of sets 34 in order to reduce switching times without detracting from full availability. In order to increase speed of operation the control function is governed by separate circuits 43 and 44, which govern routing over the network and connection of registers, respectively. The registers 47 are connected over selector 48 which is "planed" with each register serving a corresponding group of incoming junctors. The appearance of an incoming call is signalled from 30 to produce incoming junctor identity from calling number generator 40 of the threaded core kind. Such a demand is picked up by the controller 44 to cause decoder 46 to invoke class-of-service data from 39 and to mark the calling junction 30 so that it can be connected over selector 48 to a register 47 allotted by 41. The controller 44 applies checks for the plausibility of the class-of-service data and to ensure that only one junctor 30 has been marked. If checks are not satisfactory the call is abandoned and N.U. tone reverted without further attempt, if checks are satisfactory the connection to the register is made, the class-of-service data being stored in section 47a. Further check is then made to ensure that the path to the register is properly set up and to ensure that the demand for service which originally recruited the service of control 44 has been removed. If the control 44 is held for longer than a preset period the demand is disconnected and a fresh attempt at register connection is made. Faults are registered in a storage queue so that print-out does not slow down the connection process which is said to have a mean time of 20 ms. Given particulars, the register calls for the service of controller 43 which collects demands over finder 45. The controller gates access to router 42 with auxiliary route decisions made in class-of-service decoders 70, 71, and "plane" section indicator 72 in order that the route may be indicated by operation of relays in route indicator 42a. By marking a free one of the outgoing relay sets 34 in the indicated direction and marking the calling incoming junctor from the register, a free path is selected and operated from the A-switch end. The A-B and B-C links are selected by circuits 36 and 74, which indicate availability of matching links, and circuits 37 and 38 which choose from what is indicated as available. The switching network operates in the same manner as the TXE2 exchange units 1. Outgoing traffic distributer.-This also employs three stages A, B, C of relay cross-point switching matrices 49, 50, 51 between inter-link units 60 and outgoing junction circuits 68. The network is "planed" to provide full availability with each link circuit 60 having access to a "plane" of outgoing junctions. An exchange unit register 28 requiring an outgoing junction puts a demand to controller 57 of the distributer. The controller serves demands one at a time and is directed by finder/allotter 59 to serve register 28. Given requirements the controller 57 instructs router 58 which, in conjunction with "plane" section indicator 77, causes route relays in 58a to indicate the outgoing junctions 68 from which a selection can be made. Switch control circuits 52 to 56, of the TXE2 sort, select a route across the network to an outgoing junction selected by 76.